New insight: Nitrosation of n-phenyl--naphthylamine in the early stage of nitroplasticizer aging

Antioxidants are additives and used for inhibiting oxidative degradation of many polymeric materials. Likewise, to maintain long-term stability of nitroplasticizer (NP) used in the formulation of a polymer-bonded energetic material, 0.1 wt.% of an arylamine antioxidant, n-phenyl-beta-naphthylamine (PBNA) was added. Recently, the detection of PBNA nitration has brought forth the mechanistic complexity of antioxidant chemistry and created a path to understand how NP naturally degrades over time. Through a short-term aging experiment and with optimized LC-QTOF analysis, a reaction between PBNA and nitrous acid (HONO) that precedes the nitration event has been found, known as nitrosation. The identification of nitroso-PBNA has solidified the HONO elimination mechanism in NP degradation and provided new insight on the role of this arylamine antioxidant. It also shows how stabilizer reactions with key intermediate degradation species can be a contributing process in polymer degradation.